The exception informs about fail in wizard panel validation and provides
a localized description what's wrong.

Package org.openide Description

Miscellaneous general classes, especially the util classes to handle a user notifications,
displaying dialogs and wizards.

See DialogDisplayer
and referenced classes for displaying dialogs.
See NotifyDescriptor which provides
a description of a user notification to be displayed.
WizardDescriptor is the framework
provides creating and handling dialogs which leads a user step-to-step through task.
See also wizard guidebook which describes
the set of properties controls the wizard panel's layout.